Take care with volunteer potato control where sugar beet plant stand is variable, cautions Simon Fisher of Armstrong Fisher Ltd.

Reports show that emergence has been erratic on up to 40% of sugar beet acreage, particularly on lighter soils which often doubles up as potato acreage, said Fisher.

Fisher added that while surface tubers will have been killed off by the March frosts, groundkeepers emerging from depth will soon cause problems where sugar beet plants have not emerged evenly.

"Rising soil temperatures will have stimulated tubers. If germination has been variable, resulting in a range of plant sizes, proceed with caution" said Fisher.

An average density of one potato plant per square metre equates to three tonnes of lost beet yield per hectare, he points out, so good control can greatly improve margins.

Growers need to ensure that herbicide applications are not too 'hot', particularly on cotyledon beet, he advises. "Implement a 'little and often' approach to begin with based around a tank-mix of phenmedipham, ethofumesate

plus Dow Shield (clopyralid). As the crop starts to grow away a shift to more robust sprays," he added.

"The first application containing Shield should be made once groundkeepers are around 5-10cm tall. Using three applications of 0.35 litres/ha at 7-10 day intervals ensures the plant receives the full litre required for effective control," advised Fisher.

"Each application slows the growth of the haulm and so reduces competition with the developing sugar beet, the split application is essential to combat further daughter-plant emergence and prevent subsurface growth."

Shield will also benefit control of sow-thistle, fat-hen and black bindweed control. "The dry weather has increased the likelihood of these annuals being difficult to control and the addition of Dow Shield to standard post-em programmes will help in their control."